Pressure sensing means and method of a pressurized container means and system utilizing the same

ABSTRACT

A container having a pressurized fluid therein and a pressure sensing fluid operated device carried by the container for sensing pressure changes within the container. The sensing device is initially charged to same pressure level as the container and is disposed within the container so as to be substantially surrounded by the fluid therein and is thereby temperature compensated whereby pressure changes of the fluid in the container caused by temperature changes thereof are ineffective to cause sensing thereof by the sensing device as the fluid of the sensing device is at the same temperature as the fluid in the container. Such container can be utilized as the fluid pressure supply means for a vehicular air bag safety device.

United States Patent 1 1 Wagner 1 1 May 20, 1974 [75} Inventor:

[73] Assignee: Robertshaw Controls Company.

Richmond, Va.

22 Filed: Apr. 17, 1974 21 App1.No.:461,515

Related US. Application Data [62] Division of Ser, No. 322,071, Jan. 8,1973, Pat. No.

Joseph P. Wagner, Knoxville, Tenn.

[52] US. Cl. 280/150 AB [51] Int. Cl. B60r 21/10 [58] Field of Search73/393, 418; 280/150 AB; 340/242; ZOO/81.8, 83 N, 83 A, 83 R [56]References Cited UNITED STATES PATENTS 2,877,326 3/1959 Bourns 73/418 X2,899,214 8/1959 DAntini 1. 280/150 AB X 3.678758 7/1972 LawrenceZOO/81.8 3,735,376 5/1973 Kermer et a1... 340/242 3,761,655 9/1973Whelan et a1... ZOO/81.8 3,774,150 11/1973 Matsui 280/150 AB X PrimaryExaminer-Kenneth H. Betts Attorney, Agent, or FirmCandor, Candor &Tassone [57] ABSTRACT A container having a pressurized fluid therein anda pressure sensing fluid operated device carried by the container forsensing pressure changes within the container. The sensing device isinitially charged to same pressure level as the container and isdisposed within the container so as to be substantially surrounded bythe fluid therein and is thereby temperature compensated wherebypressure changes of the fluid in the container caused by temperaturechanges thereof are ineffective to cause sensing thereof by the sensingdevice as the fluid of the sensing device is at the same temperature asthe fluid in the container. Such container can be utilized as the fluidpressure supply means for a vehicular air bag safety device.

7 Claims, 16 Drawing Figures PATENI was m SHEEY 2 BF 3 PRESSURE SENSINGMEANS AND METHOD OF A PRESSURIZED CONTAINER MEANS AND SYSTEM UTILIZINGTHE SAME This is a division of application Ser. No. 322,071, filed Jan.8, 1973, now US. Pat. No. 3,818.764.

This invention relates to an improved means for sensing pressure changeswithin a pressurized container means as well as to an improved methodand system utilizing such sensing means.

It is well known that a vehicular air bag safety system has now beenprovided wherein an inflatable bag is normally disposed in a collapsed,out of the way condition and is adapted to be almost instantaneouslyinflated by fluid pressure upon an impact of the vehicle with a harmproducing object so as to protect one or more individuals in the vehiclebeing engaged by the thus inflated bag. In order to inflate such safetyair bag, a container means must be provided for storage of suchinflating fluid under pressure and in order for the system to functionproperly, the pressure in such container means must not increase ordecrease beyond a predetermined amount when that container means is at acertain temperature.

For example, such fluid storage container means can each be charged withan inert gas, such as argon, helium, and the like, or a mixture of thesame, to approximately 2400 psi at room temperature and such containermeans must be adapted to maintain the stored gas pressure so that thesame does not drop by more than approximately 200 psi or does not gainmore than 200 psi when at room temperature. Of course, such limits, aswell as others hereinafter set forth, are by way of example only and arenot intended in any manner to place restrictions on the scope of theclaimed inven tion.

It is a feature of this invention to provide means for detecting anyadverse loss or gain in the pressure in such pressurized container meanscaused by means other than temperature change, such as pressure.

changes that are caused by a leak in the container means or otherdamages of the container means.

In particular, one embodiment of this invention comprises a fluidoperated sensing means that is initially charged to the same pressurelevel as the container means and is carried by the container means insuch a manner that the sensing means is substantially surrounded by areference pressure of the fluid of the container so as to be temperaturecompensated thereby whereby any pressure changes of the fluid in thecontainer caused by temperature changes thereof are ineffective to causea sensing thereof by the sensing means as the fluid of the sensing meansis always at the same temperature as the fluid in the container. Suchsensing means comprises a fluid operated means having a movable wallinside the container with the position of that movable wall beingchanged by a pressure differential existing across the same andoperating an electric switch of a signal means to indicate when thepressure in the container means has changed from a desired value thereofto an undesired value thereof by means other than temperature change.

Thus, under extreme temperature variation conditions of the storage areafor the fluid storage container for the vehicle air bag safety system,even though the same is inside the passenger compartment, thetemperature of the fluid in the container means can reach 220 F. or 20F. and under these ambient temperature conditions, the pressure withinthe container means can build to 3400 psi or go as low as 1700 psi atthe extreme temperature conditions thereof even though the same is 2400psi at room temperature. However, since the sensing device of thisinvention is temperature com pensated by the fluid of the containeritself, so that the temperature of the fluid of the fluid operatedsensing device is the same as the temperature of the fluid in thecontainer means, such pressure changes caused by extreme temperatureconditions will not cause a false indication that the pressure withinthe container means has been adversely affected by means other thantemperature.

Accordingly, it is an object of this invention to provide sensing meansfor a pressurized container means or the like, such sensing means havingone or more of the novel features set forth above or hereinafter shownor described.

Another object of this invention is to provide an improved pressurizedcontainer means for a vehicular air bag safety means.

Another object of this invention is to provide an improved method ofsensing pressure changes in a container means having a pressurized fluidtherein.

Other objects, uses and advantages of this invention are apparent from areading of this description which proceeds with reference to theaccompanying drawings forming a part thereof and wherein FIG. 1 is aschematic view illustrating the vehicular air bag safety system of thisinvention.

FIG. 2 is an enlarged, fragmentary, cross-sectional view taken on line22 of FIG. 3 and indicates the pressure sensing means of this inventionmounted to the pressurized container means of the air bag safety systemof FIG. 1.

FIG. 3 is a fragmentary, cross-sectional view looking down on thestructure illustrated in FIG. 2 in the direction of the line 3-3 of FIG.2.

FIG. 4 is a fragmentary, cross-sectional view taken substantially online 4-4 of FIG. 2.

FIG. 5 is a fragmentary, cross-sectional view taken substantially on theline 5-5 of FIG. 4.

FIG. 6 is a view similar to FIG. 2 and illustrates another embodiment ofthis invention, FIG. 6 being taken substantially on the line 66 of FIG.7.

FIG. 7 is -a fragmentary, cross-sectional view looking downwardly on thestructure illustrated in FIG. 6 in the direction of the line 77 of FIG.6.

FIG. 8 is a fragmentary, cross-sectional view taken substantially online 88 of FIG. 6.

FIG. 9 is a view similar to FIG. 6 and illustrates another embodiment ofthis invention.

FIG. 10 is a view similar to FIG. 2 and illustrates another embodimentof this invention, FIG. 10 being taken on line I0l0 of FIG. 11.

FIG. 11 is a fragmentary, cross-sectional view taken substantially online ll--11 of FIG. 10.

FIG. 12 is a cross-sectional view taken substantially on line 1212 ofFIG. 10.

FIG. 13 is an enlarged, fragmentary, cross-sectional view taken on line13-13 of FIG. 10.

FIG. 14 is a view similar to FIG. 1 1 and illustrates still anotherembodiment of this invention.

FIG. 15 is a view similar to FIG. 14 and illustrates another embodimentof this invention.

FIG. 16 is a fragmentary view similar to FIG. 2 and illustrates anotherembodiment of this invention.

While the various features of this invention are hereinafter describedand illustrated as being particularly adaptable for providing pressuresensing means for the pressurized container means of a vehicular air bagsafety means, it is to be understood that the various features of thisinvention can be utilized singly or in any combination thereof toprovide sensing means for other devices as desired.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Further, while various configurations and structural parts areillustrated, it is to be understood that this invention is not to belimited to such configurations or structural details as otherconfigurations and structural designs can be utilized to accomplish thesame results provided by the teachings of this invention.

Referring now to FIG. 1, a vehicular air bag safety system is generallyindicated by the reference numeral 20 and comprises an air bag structure21 adapted to be normally stored in a collapsed out of the way conditionbut being adapted to be substantially instantaneously inflated asschematically illustrated in FIG. 1 by being fluidly interconnected to apressurized container means 22 by suitable means 23 that is actuated byan impact of the vehicle against a harm producing object in a mannerwell known in the art whereby the details of the same need not befurther described in order to understand the features of this invention.

The system 20 of this invention includes a signal producing device 24,such as an alarm, lamp, or other indicator, which will be activated by apressure sensing means of this invention in a manner now to be describedwhen the pressure sensing means detects an adverse change in thepressure of the fluid in the storage container means 22.

As illustrated in FIGS. 2-5, the container means 22 has a chamber 25therein adapted to be filled with pressurized fluid through a fillingtube 26 carried by a plug member 27 sealingly fixed in any suitablemanner in an opening 28 formed through a flattened portion of an endwall 29 of the container means 22. Once the chamber 25 has beenpressurized with the desired fluid to the desired pressure undercontrolled temperature conditions, the tube 26 has its lower end 30suitably closed and sealed by means 31 so as to prevent the loss offluid pressure from the chamber 25 out through the tube 26.

The plug 27 also carries the pressure sensing means of this inventionwhich is generally indicated by the reference numeral 32 and comprises ahollow ribbon-like bourdon tube 33 twisted in the manner illustrated inFIG. 2 between the opposed ends 34 and 35 thereof. The end 34 issuitably sealed closed if the tube 33 is formed from a hollow length oris already integrally closed if formed from a bulb-like length while theend 35 is sealed closed by the end plug 27 being secured thereto.However, the tube 33 has a chamber 36 therein disposed in fluidcommunication at the lower end 35 thereof with a passage 37 formed inthe plug 27 and being fluidly interconnected to another filling tube 38.The bourdon-like tube 33 is adapted to be filled with fluid pressurethrough the filling tube 38 which is then adapted to have its lower end39 sealed closed by sealing means 40 in the same manner as the fillingtube 26 previously described.

In fact, the chamber 25 of the container means 22 and the chamber 36 ofthe bourdon tube 33 can be charged through the tubes 26 and 38 at thesame time, at the same temperature and with the same fluid. In anyevent, the chamber 25 and the chamber 36 are simultaneously orseparately charged to the same fluid pressure level while at the sametemperature so that the pressure value within the chamber 36 of thebourdon tube 33 is exactly the same as the pressure value in the chamber25 of the container means 22 whereby the pressure differential acrossthe movable wall of the tube 33 initially is zero. However, anysubsequent loss of pressure from the chamber 25 or loss of pressure fromthe chamber 36 of the tube 33 will cause pressure differential to existacross the wall of the tube 33 and cause the same to tend to twist oruntwist about its longitudinal axis 41, FIG. 3, so that the end 34 willrotate in a clockwise or counterclockwise direction in FIG. 3 about theaxis 41 as the case may be. Similarly, an increase in pressure in thechamber 25 over the chamber 36 or in the chamber 36 over the chamber 25will cause a pressure differential across the wall of the tube 33 tocause the end 34 thereof to rotate about the axis 41 in a clockwise orcounterclockwise direction as the case may be.

Since the bourdon tube 33 of the sensing means 32 of this invention isdisposed within the chamber 25 of the container means 22, any outsideambient temperature changes tending to cause the pressure value of thefluid in the chamber 25 to vary, will likewise cause the pressure valueof the fluid in the chamber 36 of the sensing means 32 to vary in a likemanner so that the same, in effect, cancel each other as the bourdontube 33 is substantially completely surrounded by the fluid in thechamber 25 of the container means 22 so that pressure changes caused bytemperature will not cause the bourdon tube 33 to rotate about the axis41 as the pressure differential across the movable wall thereof remainsexactly the same whether the temperature of the fluid in the chamber 25is at an extreme hot condition or at an extreme cold condition.

The means for detecting the movement of the end 34 of the tube 33 aboutthe axis 41 thereof because of a resulting pressure differentialexisting across the wall of the tube 33 will now be described.

A conductive bracket member 42 is mounted to the conductive end plug 27by fastening members 43, FIG. 5, but is electrically insulated therefromby insulating means 44. However, the bracket 42 is electricallyinterconnected by a lead 45 to a terminal 46 passing out of the end plug27 while being electrically insulated therefrom by an insulating means47.

The terminal 46 is adapted to be interconnected by a lead 48 to one side49 of the indicator 24 while the other side 50 of the indicator 24 isadapted to be interconnected by a lead 51 to one side 52 of anelectrical power source 53 having its other side 83 interconnected toground by a lead 54.

The upper end 55 of the bracket 42 has a pair of arms 56 and 57respectively bent in the configuration illustrated in FIGS. 2 and 3 soas to be adjacent the upper end 34 of the bourdon tube 33. However, thearms 56 and 57 respectively have ends 58 and 59 disposed spaced from theend 34 of the bourdon tube 33 as illustrated in FIG. 3 so that as longas the pressure differential across the wall of the tube 33 is zero, theend 34 of the tube 33 is equally spaced from the ends 58 and 59 of thearms 56 and 57 in the manner illustrated in FIG. 3. If the pressuredifferential across the wall of the tube 33 increases, the end 34 of thetube 33 begins to rotate about the axis 41 and when such rotation issufficient to cause the end 34 of the tube 33 to contact either the end58 of the leg 56 or the end 59 of the leg 57, the indicator 24 isactivated by the sensing means 32 to indicate that an adverse loss orgain in pressure exists in the container means 22 so that the same mustbe checked.

In particular, the bracket 42 is interconnected to ground through suchcontacted leg 56 or 57, bourdon tube 33, end plug 27 and the container22 as the container 22 is itself grounded by a lead means 60 wherebycurrent is permitted to flow through the indicator 24 to cause itswarning condition.

Thus, in the operation of the system 20, as long as the pressure sensingmeans 32 is sensing that the pressure value of the fluid in the chamber25 is within acceptable limits from the initial charging pressure valuefor the chamber 25, the end 34 of the tube 33 is out of contact with thelegs 56 and 57 of the bracket means 42 so that no current can flowthrough the indicator 24 and the same remains dormant. However, upon aloss or a gain of pressure in the chamber 25 to cause the end 34 of thetube 33 to rotate about the axis 41 sufficiently to cause the end 34 tocontact one of the legs 56 or 57 of the bracket means 42, an electricalcircuit is completed across the indicator 24 so that same will indicatethat there is in sufficient pressure or too great a pressure in thechamber 25 of the container means 22 for proper operation of thevehicular air bag sensing sys tem of FIG. I. i

From the above, it can be seen that an improved pressure sensing meansand method are provided by this invention because the inside of thebourdon tube 33 is charged to the same pressure value that exists insidethe container means at a given temperature so that with a change oftemperature of the fluid within the container 22 and the resultingincrease or decrease of pressure value thereof, such temperature changeand, thus, pressure value change is equally applicable to the pressurefluid within the bourdon tube 33 to thereby cancel each other out. Thus,if a leak occurs in the container means 22, the pressure value thereofwill drop. However, the pressure in the bourdon tube 33 remains the sameand a pressure differential exists across the same causing the tube 33to deflect and make, in effect, contact with the terminal means 42completing a circuit which will give an indication on the dashboard ofthe vehicle where the indicator 24 would normally be mounted.

With the bourbon tube 33 being inside the container means 22, the tube33 feels the same temperature as the fluid in the chamber 25 of thecontainer means 22.

In a similar manner, should a leak occur from inside the bourdon tube 33to the outside of the container means 22, the other leg 56 or 57 of thebracket means 42 will be contacted by the end 34 of the tube 33producing a signal indicating that a malfunction exists in the containermeans 22.

Should it be desired to not utilize the container means 22 as a currentflow path for completing the electrical circuit for the indicator 24,the arrangement illustrated in FIGS. 6-8 can be utilized and partsthereof similar to the parts of the container means 22 and sensing means32 of FIGS. 2-5 are indicated by like reference numerals in FIGS. 6-8followed by the reference letter A.

As illustrated in FIGS. 6 and 7, the sensing means 32A for the containermeans 22A is substantially identical to the sensing means 32 previouslydescribed except that the upper end 34A of the bourdon tube 33A has aninsulative sleeve or member 61 disposed thereon and over which ismounted a .conductive sleeve or member 62 whereby the insulative sleeve61 completely electrically insulates the outer conductive sleeve 62 fromthe bourdon tube 33A.

The end plug 27A has another terminal 63 carried thereby and insulatedtherefrom in the same manner as the terminal 46A whereby the: terminal63 is adapted to be interconnected to the other side 83A of theelectrical power source 53A by a lead 64. The terminal 63 is alsointerconnected to the conductive sleeve 62 on the end 34A of the bourdontube 33A by a lead 65.

In this manner, it can be seen that when the end 34A of the bourdon tube33A has the conductive member 62 thereon in contact with one of the legs56A or 57A of the bracket means 42A, a circuit is completed to cause theindicator 24A to indicate a malfunction of the container means 22A inthe manner previously described for the container means 22 of FIG. 2 andno current flows through the wall of the container means 22.

While the sensing means 32 of this invention has been illustrated asbeing mounted in a flattened portion of the end wall 29 of the container22, it is to be understood that the sensing means 32 of this inventioncould be arranged in an angular manner if desired.

For example, reference is now made to FIG. 9 wherein another arrangementof this invention is provided and parts thereof similar to thearrangement of FIG. 2 are indicated by like reference numerals followedby the reference letter B.

As illustrated in FIG. 9, the end wall 298 of the container means 228 issubstantially dome-shaped and the end plug 27B of this invention ismounted in an opening formed through such dome-shaped end wall 29B.However, the bourdon tube 33B and bracket means 42B are angularly bentto permit the same to pass through the opening 85 and then upwardly intothe chamber 258 when the end plug 27B is mounted in place. The sensingmeans 323 functions in the same manner as the sensing means 32previously described.

While the sensing means 32, 32A and 32B have been previously describedas respectively completing a circuit when an adverse pressuredifferential is sensed by the same, it is to be understood that thesensing means could be arranged to open an electrical circuit upon anadverse pressure differential being sensed by the same.

Therefore, reference is now made to FIGS. 10-13 wherein anotherarrangement of this invention is provided andparts thereof similar tothe parts of the arrangement of FIG. 2 are indicated by like referencenumerals followed by the reference letter As illustrated in FIGS. 10 and11, the bracket means 42C is not provided with the legs 56 and 57previously described but carries a horseshoe-shaped spring member 66having a pair of arms 67 and 68 respectively disposed on opposite sidesof the upper end 34C of the bourdon tube 33C with the leg 67 carrying anelectrical contact 69 electrically insulated from the leg 67 while beingadapted to normally contact against the leg 68 in across the wall of thesame.

The bracket 42C has an upper arm 70 provided with a pair of dependingstop pins 71 and 72 extending downwardly therefrom and beingrespectively disposed adjacent L-shaped ends 73 and 74 of the springlegs 67 and 68 for a purpose hereinafter described.

The terminal 46Cfor the indicator 24C is interconnected by a lead 75 tothe contact 69. Thus, as long as the contact 69 is in contact with theleg 68 in the manner illustrated in FIG. 11, an electrical circuit iscompleted for the indicator 24C through the bracket 42C which iselectrically interconnected to the end plug 27C rather than beingelectrically insulated therefrom as is the case withthe bracket means 42previously described. Thus, since the bracket 42C is now electricallyinterconnected to the container 22C, the container 22C completes thecircuit to ground through the lead means 60C previously described. Inthis manner, the indicator 24C will indicate that no adverse pressurecondition exists as long as current flows through the same.

However, upon an adverse pressure differential being sensed by thebourdon tube 33C, the end 34C thereof rotates about the axis 41C andmoves either the leg 68 or the leg 67 away from the other leg and whilethe natural spring of the other leg is to follow such movement, therespective stop pin 71 or 72 prevents such following movement so thatthe engaged leg moves away from the other leg so that the contact 69 nowbreaks contact with the leg 68 and thus, interrupts the circuit throughthe indicator 24C so that the same will produce its indicating functionupon the breaking of the electric circuit thereto. 7

As illustrated in FIG. 13, the contact 69 for the leg 67 of the springmember 66 is electrically fastened thereto and electrically insulatedtherefrom by a rubber grommet like member 69'.

Of course, the other leg 68 could likewise carry a contact thereon whichwill be electrically insulated therefrom so that the other side 83C ofthe power source 53C could be directly interconnected thereto in thesame manner as provided by the arrangement illustrated in FIG. 6.

Thus, reference is made to FIG. 14 wherein it can be seen that the otherleg 68 has a contact 76 carried thereby and is electrically insulatedtherefrom in the same manner as the contact 69 while being adapted to beinterconnected by a lead 77 to the other side 83C of the power source53C by an additional terminal electrically insulated and carried by theend plug 27C in the same manner as the terminal 63 previously described.

While the bourdon tube 33C of the embodiments of FIGS. 11 and 14 hasbeen described as acting on only one of the legs 67 or 68 of thehorseshoe-shaped spring member 66 to move the same away from the otherleg while having stop means 71 or 72 to prevent that other leg fromfollowing such movement, it is to be understood that the bourdon tube33C itself could be utilized to act on both legs 67 and 68 to causemovement thereof away from each other to open the circuit therebetween.

For example, reference is now made to FIG. 15 wherein another embodimentof this invention comprises a container means 22D and parts thereofsimilar to the parts of the other arrangements are indicated by likereference numerals followed by the reference letter As illustrated inFIG. 15, the spring member 66D has the legs. 67D and 68D thereof soconstructed and arranged relative to the upper end 34D of the bourdontube 33D that each leg 67D and 68 D respectively has parts 78 and 79thereof disposed an equally spaced distance from the opposed ends 80 and81 of the bourdon tube 33D under normal pressure conditions so that whenthe bourdon tube 33D rotates about its longitudinal axis 41D for thereasons previously set forth, and should the same be rotating in aclockwise direction in FIG. 15, it can be seen that the opposed end 80of the tube 33D will contact the part 78 of the leg 67D while the end 81will likewise contact the part 79D of the leg 68D. Further clockwiserotation of the tube 33D will cause the legs 67D and 68D to be movedaway from each other by the rotating tube 33D so that the contacts 69Dand 76D are moved away from each other to break the circuit therebetweenwithout having one of the legs 67D or 68D being held stationary by stopmeans as in the embodiment of FIGS. 11 and 14.

Conversely, should the tube 33D be rotating in a counterclockwisedirection in FIG. 15, it can be seen that the end 81 of the tube 33Dwill contact the part 79 of the leg 67D while the end 80 thereof willcontact the part 78 of the leg 68D to cause the legs 67D and 68D to moveaway from each other upon further counterclockwise rotation of thetube'33D relative to the container 22D so that the contacts 69D and 76Dare moved away from each other to break the circuit therebetween for thereasons previously set forth.

While the various arrangements previously described each has separatefilling means for the bourdon tube and the main propellant container, itis to be understood that a single fill passage could be provided forsimultaneously charging the bourdon tube and the main container so thatthe same will have the same fluid pressure therein at all times and in asimultaneous manner. Thus, when the desired pressure level is reached,both the inside of the bourdon tube and the inside of the main containerwill be charged with the same fluid and at the same pressure levels.

For example, reference is now made to FIG. 16 wherein another embodimentof the end plug 27E for carrying the bourdon tube and switch means inthe manner previously described is illustrated and has a single filltube 82 leading to an internal passage 83 formed in the end plug 27E.The passage 83 has one branch 84 thereof leading to the exterior surface85 of the plug 27E for charging the main chamber of the main containercontaining the same whereas another branch passage 86 leads from thepassage 83 to a point that will be covered by the bourdon tube forcharging the interior chamber of such bourdon tube in the mannerpreviously described for the passage 37 of the embodiment illustrated inFIG. 2.

In order to insure that the bourdon tube will be filled at the same rateas the main chamber of the main container, the branch passage 86 can beprovided with a restrictor means 87 therein as illustrated.

Thus, it is believed that when it is desired to charge the maincontainer and the bourdon tube therefor through the end plug 27E of FIG.16, the fluid pressure source can be attached to the fill tube 82 in anysuitable manner and the same will permit the main container to becharged through the branch passage 84 while the bourdon tube is beingcharged through the branch passage 86 so that when the desired pressurelevel in the main container is reached, the same pressure level willhave been reached in the bourdon tube so that the fill tube 82 can besubsequently sealed off in the manner previously described for the filltubes 26 and 38.

However, before the tube 82 is sealed closed and after the maincontainer and bourdon tube have been charged through the respectivepassages 84 and 86, the passages 84 and 86 must be isolated from eachother and this can be accomplished by driving a ball seal into thepassage 83 to close the passage 86 from the passage 84. It is. believedthat such ball sealing can be accomplished under pressure with asuitable charging device.

Thus, it can be seen that the end plug 27D can be utilized tosimultaneously charge the main container and the pressure sensing deviceso that the same will be charged withthe same fluid, at the same timeand with the same pressure values.

Therefore. it can be seen that this invention not only provides improvedpressure sensing means and methods, but also this invention provides animproved vehicular air bag safety system.

While the form and method of the invention now preferred have beendisclosed and described as required by the patent statutes, it is to beunderstood that other forms and methods'canbe utilized and still comewithin the scope of the appended claims.

What is claimed is:

1. In combination, a vehicular air-bag safety means adapted to beinflated upon the detection of vehicular impact, a container meanshaving a pressurized fluid therein for inflating said air-bag safetymeans when fluidly interconnected thereto, fluid operated sensing meanscarried by said container means for sensing pressure changes within saidcontainer means, and detection means operatively associated with saidsensing means to indicate when said sensing means is sensing a loss or again of pressure in said container means beyond desired limits thereof,said sensing means and said container means being so constructed andarranged that said sensing means is temperature compensated by beingsubstantially surrounded by a reference pressure of said fluid of saidcontainer means so that pressure changes of said fluid in said containermeans caused by temperature changes thereof are ineffective to causesensing thereof by said sensing means as said fluid of said sensingmeans is at the same temperature as said fluid in said container means,said fluid operated sensing means and said container means having beeninitially charged with their respective pressurized fluids tosubstantially the same pressure levels.

2. A combination as set forth in claim 1 wherein said sensing meanscomprises a fluid operated bourdon tube means.

3. A combination as set forth in claim 1 wherein said fluid operatedmeans has fluid therein of the same type as the fluid in said containermeans.

4. A combination as set forth in claim 1 wherein said fluid operatedsensing means has a movable wall that moves in accordance with changesin the pressure differential across the same, said wall having saidfluid of said fluid operated means acting on one side thereof and saidreference fluid of said container means acting on the other sidethereof.

5. A combination as set forth in claim 4 wherein said detection meanscomprises an electrical switch, said movable wall of said fluid operatedsensing means being adapted to operate said electrical switch inresponse to certain movement thereof whereby said operated switchsignals a loss or a gain of pressure in said container means beyonddesired limits thereof.

6. A combination as set forth in claim 5 wherein said sensing means hassaid movable wall located inside said container means whereby saidreference pressure fluid is the fluid inside said container means actingon said other side thereof.

7. A combination as set forth in claim 6 wherein said fluid operatedsensing means comprises a twisted bourdon tube having a free end thatcomprises said movable wall and which will rotate about the longitudinalaxis of said tube upon changes in the pressure differential across thesame.

1. In combination, a vehicular air-bag safety means adapted to beinflated upon the detection of vehicular impact, a container meanshaving a pressurized fluid therein for inflating said airbag safetymeans when fluidly interconnected thereto, fluid operated sensing meanscarried by said container means for sensing pressure changes within saidcontainer means, and detection means operatively associated with saidsensing means to indicate when said sensing means is sensing a loss or again of pressure in said container means beyond desired limits thereof,said sensing means and said container means being so constructed andarranged that said sensing means is temperature compensated by beingsubstantially surrounded by a reference pressure of said fluid of saidcontainer means so that pressure changes of said fluid in said containermeans caused by temperature changes thereof are ineffective to causesensing thereof by said sensing means as said fluid of said sensingmeans is at the same temperature as said fluid in said container means,said fluid operated sensing means and said container means having beeninitially charged with their respective pressurized fluids tosubstantially the same pressure levels.
 2. A combination as set forth inclaim 1 wherein said sensing means comprises a fluid operated bourdontube means.
 3. A combination as set forth in claim 1 wherein said fluidoperated means has fluid therein of the same type as the fluid in saidcontainer means.
 4. A combination as set forth in claim 1 wherein saidfluid operated sensing means hAs a movable wall that moves in accordancewith changes in the pressure differential across the same, said wallhaving said fluid of said fluid operated means acting on one sidethereof and said reference fluid of said container means acting on theother side thereof.
 5. A combination as set forth in claim 4 whereinsaid detection means comprises an electrical switch, said movable wallof said fluid operated sensing means being adapted to operate saidelectrical switch in response to certain movement thereof whereby saidoperated switch signals a loss or a gain of pressure in said containermeans beyond desired limits thereof.
 6. A combination as set forth inclaim 5 wherein said sensing means has said movable wall located insidesaid container means whereby said reference pressure fluid is the fluidinside said container means acting on said other side thereof.
 7. Acombination as set forth in claim 6 wherein said fluid operated sensingmeans comprises a twisted bourdon tube having a free end that comprisessaid movable wall and which will rotate about the longitudinal axis ofsaid tube upon changes in the pressure differential across the same.